1. Field of the Invention
The present invention relates to a versatile production system employing a production line for producing different kinds of products.
2. Description of the Related Art
A production line involves various processes such as supplying parts, assembling the parts into products, testing the products, and conveying the products that have passed the test. When mass-producing products of a single kind, the production line may be used exclusively for producing the products. When producing different kinds of products in small quantities, there is a loss of factory space, facilities, and manpower if production lines must be prepared for the respective kinds of products.
To solve this problem, a versatile production system has been proposed. This system employs a single production line for producing different kinds of products. To flexibly produce required products in required quantities with a single production line, it is necessary to timely dispatch correct instructions to operators stationed at different locations along the production line, after taking into account the work contents, procedures, supplied parts, and quality control conditions of the locations. According to the instructions, the operators carry out tests, prepare test reports, and feed back defective products with work reports. This conventional system requires excessive time and labor in processing data and imposes a heavy load on the operators, thereby causing errors and deteriorating productivity.
The applicant of the present invention has proposed a versatile production system that flexibly produces different kinds of products in small quantities, automatically provides operators with proper instructions, informs downstream operators of data of defective upstream products, and prepares test reports.
This system separates defective products from non-defective products. The defective products are removed from the production line and conveyed to a repair station, where they are repaired and then returned to the production line.
For example, when producing disks for computers, it is necessary to write a test program to some disks. The writing process takes time. The disks are once removed from the production line, sent to a write station, and returned to the production line after the program is written to the disks. Transportation of the disks between the production line and the write station causes time loss and misplacement.
The conventional versatile production system must have a separate production line for some products whose size, in particular, height, exceeds a particular limit. This separate line may cause loss of space, facilities, and manpower.
When repairing and inspecting products supported on pallets, the pallets must be conveyed slowly. During this period, the pallets may hit one another, thereby hindering correct inspection or smooth production. In particular, when the products are computers, they are vulnerable to shock.
The production line must achieve predetermined accuracy in moving and positioning a product placed on a pallet. To provide such accuracy, the prior art gradually decreases the speed of motors, or employs servo motors, pulse motors, numerical controllers, and positioners.
When the production line employs robots for automatically assembling products, the precise positioning of a product on a pallet is very important. To provide this accuracy, conventional pallets employ jigs for positioning and fixing a product.
Numerical control positioners are very accurate but expensive. Other inexpensive positioners are not very accurate.
Before attaching a jig to a pallet, the pallet must be processed precisely. The pallets, therefore, are usually made of a metal such as aluminum. Aluminum die-cast pallets, for example, are heavy and expensive.
The positioning accuracy of a product on a pallet relative to a robot in a production line is determined by process errors in the pallet, assembling errors in a jig attached to the pallet, and dimensional errors in the product. These errors must be within respective allowances, which requires time, labor, and cost.
Empty pallets are fed individually to the start of a production line by workers. These workers must also carry out assembling work at the start of the production line. To reduce the work load of the workers, the feeding of pallets to the production line must be automated.
At an end of the production line, there is a packing terminal where products are picked up from pallets and packed. Emptied pallets are piled, and once a predetermined number of pallets are accumulated, they are transported to the start of the production line. When intervals of products conveyed to the packing terminal are long, there is extended idle time at the packing terminal. To reduce idle time, the packing terminal may deal with a plurality of production lines.
In this case, different kinds of pallets collect at the packing terminal and, therefore, workers must separate them according to type. In addition, separate conveyors must be prepared to return the pallets to the respective production lines. Accordingly, additional manpower is required to load and unload the pallets to and from the conveyors.